Osteoporosis means porous bones (bones with holes or pores inside). Such bones are less strong than normal. Osteoporosis is a description rather than a diagnosis. A diagnosis explains the cause of a person's porous bones.

Bones are alive. Every day tiny amounts of old bone are removed from areas throughout our skeletons and replaced with new bone. This process is called bone remodeling, and it is useful because it repairs microscopic cracks that normally develop in old bone. Bone remodeling can be harmful if the old bone is removed faster than the new bone is formed. When this happens over months or years, it leads to osteoporosis. Bone removal and replacement can get out of balance because old bone is removed faster than normal, or because new bone is formed slower than normal or because both occur.

Most forms of osteoporosis can be prevented or arrested. Some forms of osteoporosis can now be reversed, either partly or entirely. To learn more about rapid bone resorption, slow bone formation, osteoporosis diagnosis, and osteoporosis prevention and treatment, consult the National Osteoporosis Foundation.